A vibration control apparatus of a wind turbine generator that can be installed in a small space inside a tower, without a weight increase of the tower, and that can change the natural frequency thereof is provided. Included is a swinging rod extending in the vertical direction and suspended from beams provided on an upper part of the tower via a first universal joint; a flange part extending outward from the upper end outer surface of the swinging rod in the radial direction along the circumferential direction; a pendulum including a bob attached to the swinging rod and capable of moving up and down in the vertical direction; and a plurality of attenuation devices each of whose upper end is attached to the beams with a second universal joint and whose lower end is attached to the flange part with a third universal joint.